Cable tension preloader

ABSTRACT

Apparatus and method for maintaining tension on a cable being wound on, unwound from, or held in readiness on a drum. Two contactors grip the cable and keep it in tension relative to the drum by means of a chain drive system powered by a motor driving the drum.

nited States Patent Sturgeon et al.

CABLE TENSION PRELOADER Inventors: Larry O. Sturgeon, 615 N. Hamlin St., Orange, Calif. 92669; Leonard L. Dueker, 2241 E. Evergreen, Mesa, Ariz. 85203 Filed: Dec. 4, 1972 Appl. No.: 312,028

' US. Cl 242/54 R, 242/67.2, 242/75 Int. Cl B6511 75/00 Field of Search 242/54 R, 67.1 R, 67.2, 242/67.3 R, 75

References Cited UNITED STATES PATENTS Lazaga 242/67.2 Roseman 242/67.2

[ July 23, 1974 Smaltz 242/54 R FOREIGN PATENTS OR APPLICATIONS 566,673 4/1958 Belgium 242/54 R Primary Examiner-John W. l-luckert Assistant Examiner--Edward J. McCarthy Attorney, Agent, or Firml(nobbe, Martens, Olson, Hubbard & Bear [5 7 ABSTRACT Apparatus and method for maintaining tension on a cable being wound on, unwound from, or held in readiness on a drum. Two contactors grip the cable and keep it in tension relative to the drum by means of a chain drive system powered by a motor driving the drum.

14 Claims, 3 Drawing Figures CABLE TENSION PRELOADER BACKGROUND OF THE INVENTION a 2. The first layer of winding must be laid down carefully so that it can serve as a guide to subsequent layers. Grooves in the drum or spool surface, coupled with the level winding device and guides will assure the correct winding pattern.

3. Sufficient tension must-be provided to assure that the cable windings stay in place once they are laid down properly. This requires an arrangement for keeping the cable tightly wound on the drum regardless of whether it is being paid out, wound on the drum or spool, held in readiness or subjected to sudden release of the load. If this is not 'done, backlash and tangling will occur. This of course results in lost time in remedying the problem, and possible damage toexpensive equipment. This is particularly a problem in connection with heavy but varying cable load applications such as in sewer cleaning operations.

A common method for solving the tension problem is the use of a heavy weight on the distant end of the cable. However, this is only practical when the cable near the far end is vertical with respect to the ground so that the force of gravity keeps the material taut. If the cable cannot be configured in this manner, some device must be used to keep it in tension at the drum or spool. Further if the load is released, the tension is abruptly eliminated resulting in-backlash. Prior art in this area has been only partially effective, complex in design and not very flexible in application. There is then, a need for a simplified device that can be used in a wide variety of cable applications. This invention will meet that need.

SUMMARY OF THE INVENTION This invention uses one or more contactors to grip or squeeze a cable or similar element extending away from a support on which the cable is wound or being wound. The gripping or squeezing force is provided by means of adjustable springs, screws, weights, or other suitable means at the contactors themselves. The tension on the cable is supplied by providing a force to drive the contactors in a direction to unwind the cable. A rotational force is applied to the support in addition to that produced through the tension on the cable. The contactorsmay be driven by various means such as 1) electric or hydraulic motors providing constant torque output, (2) motors with slip clutches set to provide the desired torque, or (3) the cable drum power source together with suitable mechanical transmission means and slip clutches. In a preferred arrangement, a sprocket and chain transmission driven from the same power source that turns the drum is utilized to rotate the contactors. The power source to drive the drum is preferably a variable speed, reversible motor driven by electrical or hydraulic means. One-way drives and slip clutches automatically maintain the desired magnitude and direction of the applied tension and protect the system from excessive torque. Two one-way drives such as ratchets are utilized, one for driving in a clockwise direction, the other for driving in a counterclockwise direction. Also, two slip clutches are used,'one for each direction. These clutches are arranged to slip in the event that the desired torque value is exceeded or reversed. In every case, the direction of the tension force is at right angles to the axis of the drum and away from it. The cable is then under constant tension relative to the drum regardless of whether it is being paid out, wound on, held in readiness or subjected to sudden release of the load.

DESCRIPTION OF THE DRAWINGS Further details of the invention and its advantages are described in the Detailed Description of the Preferred Embodiment and in the attached drawings, in which:

FIG. 1 is a schematic perspective view of the cable tension preloader of the invention illustrating the overall arrangement;

FIG. 2 is a schematic elevational view of the system illustrating the manner in which the contactors are driven to apply tension to the cable when the drum is paying out or unwinding the cable;

FIG. 3 is a schematic elevational view of the system illustrating the manner in whichthe contactors are drivento apply tension to the cable when the drum is reeling in or winding the cable on the drum.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT shaft 12 driven by a suitable hydraulic or electric motor or other suitable power source 14. A flexible element such as a cable 16 is wound on the drum 10. The power source 14 also drives a chain and sprocket transmission means generally indicated at 15 utilized to rotate a cableguide assembly 22 and a pair of cable contactors l8 and 20, in the form of elongated rollers.

More specifically, a sprocket 24 fixed to the shaft 12 drives a chain 26, which inturn drives a sprocket 28 mounted on a shaft 30. An additional pair of sprockets 32 and 34 are mounted on the ends of the shaft 30. A chain 36 mounted on the sprocket 34 drives a pair of sprockets 38 and 40 respectively mounted on spaced parallel drive shafts 42 and 44. The drive shaft 44 is formed in two sections 44a and 44b connected by a one-way drive or clutch 46, which will transmit torque in the counterclockwise direction as viewed in FIG. 1. A sprocket 48 is mounted on the end of the driven shaft section 44b through a slip clutch 50. The sprocket 48 drives a chain 52 which is further mounted on an idler sprocket 54; a sprocket 56, mounted on the end of a shaft 58 supporting the roller contactor 20; and a sprocket 60, mounted on the end of a shaft 62, supporting the lower roller contactor 18.

Similar to the shaft 44, the shaft 42 is formed in two sections'42a and 42b connected by one-way drive or clutch 64. However, the clutch 64 is arranged to transmit torque in the clockwise direction, opposite to that of the clutch 46. A sprocket 66 is mounted on the end of the driven shaft section 42b through a slip clutch 68. A chain 70 is driven by the sprocket 66 and in turn drives a sprocket 72 mounted on the shaft 58 carrying the upper roller contactor 20, and spaced from the sprocket 56 on that same shaft.

As can be seen the roller contactor shafts 58 and 62 are mounted on brackets 74 which are loaded by a pair of springs 76 to grip or squeeze the cable 16.

The cable 16 is guided to the roller contactors 18 and 20 by a sheave 78 rotatably mounted on a support 80 forming a part of the cable guide assembly 22. A pair of spaced rods 82 extend upwardly from the support 80 to guide the cable. The support 80 is mounted on and driven transversely by a spirally grooved roller 84 mounted on a shaft 86. A drive sprocket 88 on the shaft 86 is driven by a chain 90 which in turn is driven by the sprocket 32 on the shaft 30.

OPERATION In operation, consider first the condition wherein the cable 16 is being paid out or unwound from the drum 10. Referring to FIGS. 1 and 2, the power source 14 rotates the drive shaft 12 in the counterclockwise direction which results in the drum rotating in the same direction unwinding the cable. There is now needed a force to take the cable 16 away from the drum. This is provided by torque introduced through the upper and lower contactors 18 and 20. The main sprocket 24 and the chain 26 are also driven counterclockwise, which, in turn, rotates the drive shaft 30, causing the sprocket 34, the chain 36, the sprockets 38 and 40, and the shaft sections 42a and 44a to turn counterclockwise. The one-way drive 64 in the shaft 42 does not transmit torque when the sprocket 38 rotates in the counterclockwise direction. Therefore, the shaft section 42b is not rotated by the section 42a. However, the one way drive 46 is effective in the counterclockwise direction, and thus the shaft section 44b is rotated causing the slip clutch 50, the sprocket 48 and the chain 52 to rotate in the counterclockwise direction. Consequently, the upper contactor drive sprocket 56 and the contactor 20 are turned clockwise and the lower contactor drive sprocket 60 and lower contactor 18 are driven counterclockwise. This rotation, coupled with the squeezing force between the upper and lower contactors 20 and 18 produces tension in the unwind direction on the cable 16, taking the cable away from the drum and paying it out with the working load, all as indicated by the arrows in FIG. 2. The amount of squeezing force between the upper and lower contactors and 18 can be adjusted by the adjustable pressure springs 76 to prevent slippage between the cable and the contactors.

Note that the cable does not unwind from the drum 10 as fast as the contactors 20 and 18 would urge the cable to move. This is accomplished by selecting the sprocket sizes to drive the contactors l8 and 20 at a rate which will result in a cable speed (feet per minute) through the contactors l8 and 20 which is greater than 4 erting a pull on the cable. In every case, the cable 16 remains taut on the drum and is supplied to the working load in an orderly fashion.

Returning to FIG. 1, consider the effect of paying out the cable 16 on the remainder of the drive mechanism. When the contactor drive chain 52 turns counterclockwise, the upper contactor drive sprocket 56 turns clockwise. This turns sprocket 72 and contactor drive chain 70, sprocket 66, slip clutch 68, and shaft 42b clockwise. However, at this time the drive shaft 42a is turned counterclockwise by the sprocket 38. The oneway ratchet drive 64 is between these two rotational forces and decouples them, because it is engaged only when the sprocket 38 and the drive shaft 42a turn clockwise.

The power source 14 also drives the chain 90 which rotates the grooved roller 84 causing the guide assembly 22 to be moved transversely to assist smooth removal of the cable.

Concluding our discussion of the counterclockwise operation, these are the two conditions necessary for proper operation: (1) The upper and lower contactors 20 and 18 must have sufficient grip or squeezing force on the cable 16 to prevent slippage; and (2) The speed of the upper and lower contactors 20 and 18 must be such that they urge the cable 16 off the drum faster than the rotation of the drum is unwinding it. This is arranged by proper selection of the various sprocket diameters.

Consider now the operation of the apparatus when the cable 16 is being wound on the drum in connection with FIGS. 1 and 3. In this condition, the power source 14 rotates clockwise, drive shaft 12 turns the drum clockwise and a cable winding force is provided. If the load is small a drag or unwinding force is needed to keep the cable taut on the drum and taut between the drum and the contactors.

Clockwise rotation of the drive shaft 12 turns the main sprocket 24, the chain drive 26, the sprocket 28, the drive shaft 30, the sprocket 34, 38 and 40; the chain 36 and the drive shaft sections 42a and 44a in the same direction. (This also reverses movement of the level winding and guide assembly 22 to assist winding the cable 16 in accordance with the preset pattern on the roller 84.) Oneway drive 46 slips, but the one-way drive 64 is now driven causing the shaft section 42b to rotate. Thus, the contactor drive chain 70 through the slip clutch 68 and the sprocket 66 is urged to rotate in the clockwise direction driving the upper contactor 20 clockwise or in a cable unwinding direction. Also, the upper sprocket 56, through the chain 52, urges the lower contactor sprocket and the contactor 18 to rotate counterclockwise or in a cable unwinding direction. This unwinding force is shown schematically in FIG. 3 by the dotted arrow. Note that the contactors 18 and 20 are urged to rotate in the same direction as when the power source 14 was turning counterclockwise, thus again providing an unwinding force on the cable 16. Because the winding force through the drum is greater than the unwinding force produced through the contactors and is in the opposite direction, the cable moves in the winding direction and the contactors 18 and 20 are actually moved in the cable winding direction, as indicated in FIG. 3 by the solid arrows and in opposition to the force produced through the chain transmission.

Thus the chain 70 and the sprocket 66 also rotate counterclockwise or in the cable'winding direction.

Since the shaft section 42b is being driven clockwise the slip clutch 68 slips to accommodate these opposite forces in the drive system.

The chain 52 and sprocket 48 are being driven by the cable clockwise which produces a clockwise force on the slip clutch 50 and the shaft section 44b. The drive appearing at sprocket 40 and drive shaft section 44a is in the clockwise direction also and the one-way drive 46 is not effective to drive in the clockwise direction. Thus this movement is accommodated. Further, if the shaft section 44b should be driven clockwise at'a rate faster than the section 44a and could then attempt to drive the section 44a through the one-way drive 46, the slip clutch 50 would function to protect the mechanism. Thus, if the load should break the cable, backlash cannot occur because of the presence of the unwinding force in the cable produced through the contactors.

The apparatus described provides a tension force on the cable being wound, unwound, or held in readiness on the spool. This tension force is self regulating in the sense that the rotational rate of the contactors changes in proportion to the rotational rate of the drum, since both are driven by the same source. This tension force is actually set by the adjustment of the adjustable slip clutches 50 and 66; however, the adjustment shall not provide atension force such that the friction between the cable and the contactors is exceeded.

What is claimed is:

1. Apparatus for maintaining tension on a flexible element, being wound or unwound, comprising:

rotatably mounted support meanson which the element is wound or unwound; and contactor means for gripping the element and applying an unwinding force to the element while either a winding or unwinding force is applied to the support means in the addition to that produced through said contactor means, the unwinding force being applied through the contactor means urging the element to unwind at a faster rate than said unwinding force applied to the support means. 2. The apparatus of claim 1 wherein the contactor means are elongated rollers which grip the element with sufficient force to prevent slippage between the element and the contactor means.

3. The apparatus of claim 1 including a single power source used to drive both the support means and the contactor means.

4. The. apparatus of claim 1 including guide means for maintaining the element approaching the support means at approximately 90 to the rotational axis of the support means.

5. The apparatus of claim 1 including clutch means to accommodate the difference between the forces and speeds applied through the contactor means and those applied through the support means. v

6. Apparatus for handling cable or similar elements comprising: a storage drum with cable wound thereon; a power source for rotating the drum; contactor means engaging a cable extending from the drum;

means for causing the contactor means to engage the cable with sufficient force to prevent slippage between the cable and the contactor means. as the cable passes through the contactor means;

means for driving the contactor means in a manner to urge the cable to unwind from the drum; and

force transmission means driven by the drum drive means and forming the means for urging the contactor means to rotate, said transmission means including:

a first transmission shaft driven by the drum drive means having a driving section and a driven section interconnected by a one-way drive, the driven section being connected to drive the contactors in a cable unwinding direction when the drum is driven in the cable unwinding direction;

a second transmission shaft driven by the drum drive means, said second shaft having a driving section and a driven section interconnected by a one-way drive, the driven section being connected to drive the contactor means in a direction to unwind the cable when the drum is driven in the cable winding direction; and

slip clutch means permitting the contactor means to be rotated by the cable regardless of the unwinding force produced through the transmissionshafts.

7. Apparatus for handling cable or similar elements comprising: i

a storage drum with cable wound thereon;

a power source for rotating the drum;

contactor means engaging a cable extending from the drum;

means for causing the contactor means to engage the cable with sufficient force to prevent slippage'between the cable and the contactor means as the cable passes through the contactor means;

means for driving the contactor means in a manner to urge the cable to unwind from the drum; and

transmission means driven by the drum drive means and forming the means for urging the contactors to rotate, said transmission means including:

first and second spaced, parallel transmission shafts driven by the drum drive means, each shaft having a driving section and a driven section interconnected by a one-way drive, the one-way drive being arranged such that when the drum is rotated in one direction, the driven shaft section of said first shaft is rotated through its one-way drive while the driven shaft section of the second shaft is not driven through its one-way drive, and when the drum is rotated in the other direction, driven shaft section of the shaft is rotated through its one-way drive while the driven shaft section of the first shaft is not driven through its one way drive;

means connecting said first driven shaft section to urge the contactor means to rotate in a manner to urge the cable to unwind;

means connecting said second driven shaft section to rotate the contactor means in a manner to urge the cable to unwind; and

slip clutch means included in said connecting means to permit the contactor means to be rotated by the cable regardless of the forces transmitted by the connecting means.

. 8. The apparatus of claim 7 wherein said contactor means comprises a pair of rotary contactors mounted in opposing relation on separate shafts so that cable passes between the contactors; and said means connecting said shaft sections to the contactor means includes:

a sprocket mounted on each of the shafts supporting said contactors;

an idler sprocket positioned adjacent to and aligned with the sprockets on the contactor shafts, a sprocket mounted on the driven shaft section of said first transmission shaft, and a chain interconnecting said sprockets in a manner to urge the retary contactors to move in the direction to unwind the cable;

a second sprocket mounted on one of the shafts supporting one of the contactors, a sprocket mounted on the driven shaft section of said second transmission shaft, and a chain interconnecting said second sprocket and said sprocket on the driven section of said second shaft; and

said slip clutches connect said driven shaft sections to their sprockets.

9. The apparatus of claim 4 wherein said contactor means comprises a pair of elongated rollers, and said guide means includes a support structure extending adjacent the contactor rollers, means mounted on the support structure for guiding the flexible element to and from the contactor rollers, and means other than the flexible element for driving the support structure parallel to the contactor rollers.

10. A method of facilitating the winding or unwinding of a flexible element, such as a cable, on a rotatably mounted support comprising:

passing the element between contactor means which applies a pinching force to the element sufficient to prevent slippage between the contactor means and the element; and

applying a force urging the contactor means to move the element in an unwinding direction while selectively driving the support in either the winding or unwinding direction.

11. The method of claim 10 utilizing the means for driving the support to also drive the contactor means.

12. The method of claim 10 wherein the contactor means urge the element to unwind at a linear rate faster than the linear rate caused by the support.

13. A method of preventing backlash or fouling of cable on a storage drum which can be selectively rotated in a cable winding or unwinding direction, comprising the steps of:

passing the cable between a pair of rotatably mounted cable contactors;

applying a squeezing force to the cable through the contactors sufficient to prevent slippage between the contactors and the cable; and

applying a rotational force to at least one of the contactors to urge the cable to move in an unwinding direction while the drum is being rotated in either the cable winding or unwinding direction, said contactors urging the cable to unwind at a linear rate faster than the unwinding linear rate caused by the unwinding rotating force applied directly to the drum, the contactor rotational force being applied through clutch means which accommodates the differential in rate or direction between the drum force and the contactor force.

14. The method of claim 13 wherein the linear rate of cable movement urged by the contactors increases as the unwinding linear rate produced by the drum increases. 

1. Apparatus for maintaining tension on a flexible element, being wound or unwound, comprising: rotatably mounted support meAns on which the element is wound or unwound; and contactor means for gripping the element and applying an unwinding force to the element while either a winding or unwinding force is applied to the support means in the addition to that produced through said contactor means, the unwinding force being applied through the contactor means urging the element to unwind at a faster rate than said unwinding force applied to the support means.
 2. The apparatus of claim 1 wherein the contactor means are elongated rollers which grip the element with sufficient force to prevent slippage between the element and the contactor means.
 3. The apparatus of claim 1 including a single power source used to drive both the support means and the contactor means.
 4. The apparatus of claim 1 including guide means for maintaining the element approaching the support means at approximately 90* to the rotational axis of the support means.
 5. The apparatus of claim 1 including clutch means to accommodate the difference between the forces and speeds applied through the contactor means and those applied through the support means.
 6. Apparatus for handling cable or similar elements comprising: a storage drum with cable wound thereon; a power source for rotating the drum; contactor means engaging a cable extending from the drum; means for causing the contactor means to engage the cable with sufficient force to prevent slippage between the cable and the contactor means as the cable passes through the contactor means; means for driving the contactor means in a manner to urge the cable to unwind from the drum; and force transmission means driven by the drum drive means and forming the means for urging the contactor means to rotate, said transmission means including: a first transmission shaft driven by the drum drive means having a driving section and a driven section interconnected by a one-way drive, the driven section being connected to drive the contactors in a cable unwinding direction when the drum is driven in the cable unwinding direction; a second transmission shaft driven by the drum drive means, said second shaft having a driving section and a driven section interconnected by a one-way drive, the driven section being connected to drive the contactor means in a direction to unwind the cable when the drum is driven in the cable winding direction; and slip clutch means permitting the contactor means to be rotated by the cable regardless of the unwinding force produced through the transmission shafts.
 7. Apparatus for handling cable or similar elements comprising: a storage drum with cable wound thereon; a power source for rotating the drum; contactor means engaging a cable extending from the drum; means for causing the contactor means to engage the cable with sufficient force to prevent slippage between the cable and the contactor means as the cable passes through the contactor means; means for driving the contactor means in a manner to urge the cable to unwind from the drum; and transmission means driven by the drum drive means and forming the means for urging the contactors to rotate, said transmission means including: first and second spaced, parallel transmission shafts driven by the drum drive means, each shaft having a driving section and a driven section interconnected by a one-way drive, the one-way drive being arranged such that when the drum is rotated in one direction, the driven shaft section of said first shaft is rotated through its one-way drive while the driven shaft section of the second shaft is not driven through its one-way drive, and when the drum is rotated in the other direction, driven shaft section of the shaft is rotated through its one-way drive while the driven shaft section of the first shaft is not driven through its one way drive; means connecting said first driven shaft section to urge the contactor means to rotate in a manner to urge the cable to unwind; means connecting said second driven shaft section to rotate the contactor means in a manner to urge the cable to unwind; and slip clutch means included in said connecting means to permit the contactor means to be rotated by the cable regardless of the forces transmitted by the connecting means.
 8. The apparatus of claim 7 wherein said contactor means comprises a pair of rotary contactors mounted in opposing relation on separate shafts so that cable passes between the contactors; and said means connecting said shaft sections to the contactor means includes: a sprocket mounted on each of the shafts supporting said contactors; an idler sprocket positioned adjacent to and aligned with the sprockets on the contactor shafts, a sprocket mounted on the driven shaft section of said first transmission shaft, and a chain interconnecting said sprockets in a manner to urge the rotary contactors to move in the direction to unwind the cable; a second sprocket mounted on one of the shafts supporting one of the contactors, a sprocket mounted on the driven shaft section of said second transmission shaft, and a chain interconnecting said second sprocket and said sprocket on the driven section of said second shaft; and said slip clutches connect said driven shaft sections to their sprockets.
 9. The apparatus of claim 4 wherein said contactor means comprises a pair of elongated rollers, and said guide means includes a support structure extending adjacent the contactor rollers, means mounted on the support structure for guiding the flexible element to and from the contactor rollers, and means other than the flexible element for driving the support structure parallel to the contactor rollers.
 10. A method of facilitating the winding or unwinding of a flexible element, such as a cable, on a rotatably mounted support comprising: passing the element between contactor means which applies a pinching force to the element sufficient to prevent slippage between the contactor means and the element; and applying a force urging the contactor means to move the element in an unwinding direction while selectively driving the support in either the winding or unwinding direction.
 11. The method of claim 10 utilizing the means for driving the support to also drive the contactor means.
 12. The method of claim 10 wherein the contactor means urge the element to unwind at a linear rate faster than the linear rate caused by the support.
 13. A method of preventing backlash or fouling of cable on a storage drum which can be selectively rotated in a cable winding or unwinding direction, comprising the steps of: passing the cable between a pair of rotatably mounted cable contactors; applying a squeezing force to the cable through the contactors sufficient to prevent slippage between the contactors and the cable; and applying a rotational force to at least one of the contactors to urge the cable to move in an unwinding direction while the drum is being rotated in either the cable winding or unwinding direction, said contactors urging the cable to unwind at a linear rate faster than the unwinding linear rate caused by the unwinding rotating force applied directly to the drum, the contactor rotational force being applied through clutch means which accommodates the differential in rate or direction between the drum force and the contactor force.
 14. The method of claim 13 wherein the linear rate of cable movement urged by the contactors increases as the unwinding linear rate produced by the drum increases. 